Warm the olive oil. Add the diced onions and bell pepper and saute for 3–4 minutes. Stir in the garlic.Crumble the ground beef into the skillet and cook.
Sprinkle the taco seasoning on top of the meat, then add diced tomatoes, and tomato paste . Remove the skillet from the heat and add the cream cheese. Add the cooked noodles and toss until coated.
Add spaghetti into the prepared casserole dish and top with the shredded cheese. Bake for 20 to 25 minutes.Garnish with fresh cilantro, fresh diced tomatoes, or sliced green onions, if desired.